Re: Single or multi hole off-axis filters?

From: Jon Isaacs (jonisaacs_at_aol.com)
Date: 06/10/04 

Date: 10 Jun 2004 00:15:26 GMT

>Multiple images when out of focus, but a single image when in focus.
>If it's a two-hole mask, with the holes aligned east-west, there are
>are two star images per star, with the images aligned north-south (as
>I recall).

So how accurately do the holes have to be cut to provide that alignment?

I know when I am doing CCD imaging with my little newt, I focus by making sure
the diffraction spikes from the spider vanes are nice and sharp.

jon

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